1. Field of the Invention
The present invention relates to a lens unit construction for a motion picture projector.
2. Description of the Prior Art
In case of almost all of the conventional motion picture projectors, the device for holding and adjusting the motion picture projection lens construction is generally designed so that the lens construction holding device for holding the lens construction adjustable along the optical axis is fixed on a part of the motion picture projector or is formed on the projector as one body. The focus adjusting member is typically provided on the mantle cover for the lens construction to be fixed on the motion picture projector body so as to cover the construction holding frame and so as to be operable from outside whereby the cam follower pin provided on the fixed external cylinder of the motion picture projecting lens construction is engaged into the cam groove for the focus adjustment provided on the adjustment member in such a manner that by operating the adjustment member the motion picture lens construction is slidably moved relative to the construction holding frame so as to adjust the focus.
In motion picture projectors designed as mentioned above the lens construction is first brought into the construction holding frame, while the cam follower pin is permitted to fall into the slide guide hole provided in the construction holding frame. The adjusting member is then mounted on the construction holding frame or the mantle cover undismountably. The top of the cam follower pin projecting out of the guide hole is caught in the cam groove. Assembly is comparatively troublesome and inefficient so that it is not suited for mass production. Production cost for such a projector are therefore high, which is not profitable.
On the other hand, it is also necessary that the operator be able to take the motion picture lens construction out of the projector body so that the operator might be able to clean the surface of the lens giving to the film or to exchange the lens. The above mentioned construction is very inconvenient for the operator to accomplish this.